With increasing development of scientific technologies, the method for storing documents is changed from the filing of paper documents to the storage of the documents' electronic files. Generally, a scanning apparatus is a device for scanning the contents of paper documents into electronic files, so that the electronic files may be further spread, managed or stored.
In the early stage, the scanning apparatus can only scan one side of the document. For scanning both sides of the document, after one side of the document has been scanned, the document should be manually turned over so as to scan the other side of the document. However, the process of manually turning over the document is troublesome. For solving the drawbacks, an automatic document feeder is usually integrated with a flatbed scanning portion. Consequently, a stack of documents can be successively transported by the automatic document feeder and a duplex scanning operation can be performed by the flatbed scanning portion the without the need of manually turning over the documents.
Conventionally, the automatic document feeder and the flatbed scanning portion are integrated into an image scanning apparatus. Hereinafter, a conventional image scanning apparatus will be illustrated with reference to FIG. 1. FIG. 1 is a schematic side view illustrating the automatic document feeder and the flatbed scanning portion of a conventional image scanning apparatus. This conventional image scanning apparatus is disclosed in for example U.S. Pat. No. 6,792,241. As shown in FIG. 1, the conventional image scanning apparatus 1 comprises a document pick-up module 10, an upper cover 11, a separation pad 12, a document stopper 13, a conveying channel 14, a document input tray 15, a document discharge tray 16, plural conveying roller assemblies 17, and a document discharge roller assembly 18. The document input tray 15 is used for placing plural documents S thereon. The document discharge tray 16 is disposed under the document input tray 15. After the plural documents S are scanned, the scanned documents S are placed on the document discharge tray 16. The document pick-up module 10 is disposed under the upper cover 11 for transporting the plural documents S from the document input tray 15 into the conveying channel 14. The document pick-up module 10 comprises a pick-up roller 101 and a separation roller 102. The pick-up roller 101 is used for contacting the plural documents S, thereby transporting the plural documents S. The separation roller 102 is used for separating the uppermost document S from the underlying documents, so that only a single document S is fed into the conveying channel 14. The separation pad 12 is disposed under the separation roller 102 for providing a friction force to the document S that is in contact with the separation pad 12, thereby facilitating the separation roller 102 to transport a single document S into the conveying channel 14.
The document stopper 13 is disposed under the document pick-up module 10. The document stopper 13 may be selectively in a protruded status or a stored status. In a case that the document stopper 13 is in the protruded status, the plural documents S are stopped from being fed into the conveying channel 14. Whereas, in a case that the document stopper 13 is in the stored stats, the plural documents S can be fed into the conveying channel 14 without being stopped by the document stopper 13. The plural conveying roller assemblies 17 are disposed in the conveying channel 14 for moving the plural documents S along the conveying channel 14. The document discharge roller assembly 18 is located beside the document discharge tray 16 for ejecting the plural documents S to the document discharge tray 16. The flatbed scanning portion 2 is disposed under the automatic document feeder 1. The flatbed scanning portion 2 has a scanning module 20. The conveying channel 14 goes through a region over the scanning module 20. When the document S is transported across the region over the scanning module 20, the document S is scanned by the scanning module 20.
Hereinafter, the operations of the automatic document feeder 1 will be illustrated with reference to FIGS. 1, 2 and 3. FIG. 2 is a schematic partial side view illustrating the conventional automatic document feeder in a standby mode. In a case that the conventional automatic document feeder is operated in the standby mode, the document pick-up module 10 is swung upwardly toward the upper cover 11 by using the separation roller 102 as the fulcrum. Meanwhile, the document stopper 13 is in the protruded status to block the conveying channel 14, so that the plural documents S are stopped from being fed into the conveying channel 14.
Please refer to FIGS. 1 and 3. FIG. 3 is a schematic partial side view illustrating the conventional automatic document feeder in a document-feeding mode. In a case that the conventional automatic document feeder is operated in the document-feeding mode, the document pick-up module 10 is swung downwardly to be distant from the upper cover 11 by using the separation roller 102 as a fulcrum. Meanwhile, the document stopper 13 is in the stored status, and the conveying channel 14 is not blocked. Consequently, the pick-up roller 101 of the document pick-up module 10 is contacted with the plural documents S on the document input tray 15, thereby transporting the plural documents S. During the process of transporting the plural documents S by the pick-up roller 101, the uppermost document S of the plural documents S are contacted with the separation roller 102, and the lowermost document S of the plural documents S are contacted with the separation pad 12. In response to the friction provided by the separation pad 12, the uppermost document S is separated from the underlying documents and fed into the conveying channel 14.
Next, the document S is transported by the plural conveying roller assemblies 17, so that the document S is moved along the conveying channel 14. When the document S is moved across the region over the scanning module 20, the document S is scanned by the scanning module 20, so that a scanned image of the document S is acquired. Afterwards, the scanned document S is transported by the document discharge roller assembly 18 to be ejected to the document discharge tray 16. Under this circumstance, the scanning operation of the uppermost document S has been completed. The processes of scanning the remaining documents S are similar to the above process, and are not redundantly described herein.
However, the conventional automatic document feeder still has some drawbacks. In a case that the automatic document feeder 1 is operated in the standby mode and the action of picking up the document is not done, the document pick-up module 10 is swung upwardly toward the position near the upper cover 11. For allowing the document pick-up module 10 to be stayed at the position near the upper cover 11, the document pick-up module 10 should acquire sufficient electricity from the automatic document feeder 1. Generally, for saving electricity, the commercially available automatic document feeder may be operated in a power-saving mode or a sleep mode. In a case that the conventional automatic document feeder 1 is operated in the power-saving mode or the sleep mode, the electricity is usually insufficient to allow the document pick-up module 10 to be stayed at the position near the upper cover 11. That is, since the document pick-up module 10 fails to be stayed at the position near the upper cover 11 in the power-saving mode or the sleep mode, the gravity of the document pick-up module 10 may allow the document pick-up module 10 to be naturally and downwardly swung and sustained against the document stopper 13. Under this circumstance, the document stopper 13 is readily changed from the protruded status to the stored status, so that the functions of blocking the conveying channel 14 and stopping the documents is lost.
If the user does not realize that the conventional automatic document feeder 1 is operated in the power-saving mode or the sleep mode at this moment, after the plural documents are placed on the document input tray 15, the plural documents are readily introduced into the conveying channel 14. The reason is because the conveying channel 14 is not effectively blocked by the document stopper 13. After the conventional automatic document feeder 1 is enabled and the electricity provided to the document pick-up module 10 is normal, the document stopper 13 is possibly stopped by the document within the conveying channel 14. Under this circumstance, the document stopper 13 fails to be protruded out, and thus the function of stopping the documents is lost. Consequently, when the document pick-up module 10 is operated in the document-feeding mode, a multi-feeding problem of simultaneously feeding two or more documents or a problem unable to feed any document (i.e. a non-feeding problem) may occur. Therefore, there is a need of providing an improved automatic document feeder for avoiding an erroneous action of the document pick-up module.